Begin implementing core msc2836 logic

internal/mscs/msc2836/msc2836.go

@@ -20,6 +20,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"net/http"
+	"sort"
 
 	"github.com/matrix-org/dendrite/clientapi/jsonerror"
 	"github.com/matrix-org/dendrite/internal/hooks"
@@ -35,14 +36,49 @@ type eventRelationshipRequest struct {
 	MaxDepth        int    `json:"max_depth"`
 	MaxBreadth      int    `json:"max_breadth"`
 	Limit           int    `json:"limit"`
-	DepthFirst      bool   `json:"depth_first"`
-	RecentFirst     bool   `json:"recent_first"`
-	IncludeParent   bool   `json:"include_parent"`
-	IncludeChildren bool   `json:"include_children"`
+	DepthFirst      *bool  `json:"depth_first"`
+	RecentFirst     *bool  `json:"recent_first"`
+	IncludeParent   *bool  `json:"include_parent"`
+	IncludeChildren *bool  `json:"include_children"`
 	Direction       string `json:"direction"`
 	Batch           string `json:"batch"`
 }
 
+func (r *eventRelationshipRequest) applyDefaults() {
+	if r.Limit > 100 || r.Limit < 1 {
+		r.Limit = 100
+	}
+	if r.MaxBreadth == 0 {
+		r.MaxBreadth = 10
+	}
+	if r.MaxDepth == 0 {
+		r.MaxDepth = 3
+	}
+	t := true
+	f := false
+	if r.DepthFirst == nil {
+		r.DepthFirst = &f
+	}
+	if r.RecentFirst == nil {
+		r.RecentFirst = &t
+	}
+	if r.IncludeParent == nil {
+		r.IncludeParent = &f
+	}
+	if r.IncludeChildren == nil {
+		r.IncludeChildren = &f
+	}
+	if r.Direction != "up" {
+		r.Direction = "down"
+	}
+}
+
+type eventRelationshipResponse struct {
+	Events    []gomatrixserverlib.ClientEvent `json:"events"`
+	NextBatch string                          `json:"next_batch"`
+	Limited   bool                            `json:"limited"`
+}
+
 // Enable this MSC
 func Enable(base *setup.BaseDendrite, monolith *setup.Monolith) error {
 	db, err := NewDatabase(&base.Cfg.MSCs.Database)
@@ -70,11 +106,108 @@ func Enable(base *setup.BaseDendrite, monolith *setup.Monolith) error {
 					JSON: jsonerror.BadJSON(fmt.Sprintf("invalid json: %s", err)),
 				}
 			}
+			// Sanity check request and set defaults.
+			relation.applyDefaults()
+			var res eventRelationshipResponse
+			var returnEvents []*gomatrixserverlib.HeaderedEvent
+
+			// Can the user see (according to history visibility) event_id? If no, reject the request, else continue.
+			event := getEventIfVisible(req.Context(), relation.EventID, device.UserID)
+			if event == nil {
+				return util.JSONResponse{
+					Code: 403,
+					JSON: jsonerror.Forbidden("Event does not exist or you are not authorised to see it"),
+				}
+			}
+
+			// Retrieve the event. Add it to response array.
+			returnEvents = append(returnEvents, event)
+
+			if *relation.IncludeParent {
+				if parentEvent := includeParent(req.Context(), event, device.UserID); parentEvent != nil {
+					returnEvents = append(returnEvents, parentEvent)
+				}
+			}
+
+			if *relation.IncludeChildren {
+				remaining := relation.Limit - len(returnEvents)
+				if remaining > 0 {
+					children, resErr := includeChildren(req.Context(), db, event.EventID(), remaining, *relation.RecentFirst, device.UserID)
+					if resErr != nil {
+						return *resErr
+					}
+					returnEvents = append(returnEvents, children...)
+				}
+			}
+
+			remaining := relation.Limit - len(returnEvents)
+			var walkLimited bool
+			if remaining > 0 {
+				// Begin to walk the thread DAG in the direction specified, either depth or breadth first according to the depth_first flag,
+				// honouring the limit, max_depth and max_breadth values according to the following rules
+				var events []*gomatrixserverlib.HeaderedEvent
+				events, walkLimited = walkThread(req.Context(), db, remaining)
+				returnEvents = append(returnEvents, events...)
+			}
+			res.Events = make([]gomatrixserverlib.ClientEvent, len(returnEvents))
+			for i, ev := range returnEvents {
+				res.Events[i] = gomatrixserverlib.HeaderedToClientEvent(*ev, gomatrixserverlib.FormatAll)
+			}
+			res.Limited = remaining == 0 || walkLimited
+
 			return util.JSONResponse{
 				Code: 200,
-				JSON: struct{}{},
+				JSON: res,
 			}
 		}),
 	).Methods(http.MethodPost, http.MethodOptions)
 	return nil
 }
+
+// If include_parent: true and there is a valid m.relationship field in the event,
+// retrieve the referenced event. Apply history visibility check to that event and if it passes, add it to the response array.
+func includeParent(ctx context.Context, event *gomatrixserverlib.HeaderedEvent, userID string) (parent *gomatrixserverlib.HeaderedEvent) {
+	parentID, _ := parentChildEventIDs(event)
+	if parentID == "" {
+		return nil
+	}
+	return getEventIfVisible(ctx, parentID, userID)
+}
+
+// If include_children: true, lookup all events which have event_id as an m.relationship
+// Apply history visibility checks to all these events and add the ones which pass into the response array,
+// honouring the recent_first flag and the limit.
+func includeChildren(ctx context.Context, db Database, parentID string, limit int, recentFirst bool, userID string) ([]*gomatrixserverlib.HeaderedEvent, *util.JSONResponse) {
+	children, err := db.ChildrenForParent(ctx, parentID)
+	if err != nil {
+		util.GetLogger(ctx).WithError(err).Error("failed to get ChildrenForParent")
+		resErr := jsonerror.InternalServerError()
+		return nil, &resErr
+	}
+	var childEvents []*gomatrixserverlib.HeaderedEvent
+	for _, child := range children {
+		childEvent := getEventIfVisible(ctx, child, userID)
+		if childEvent != nil {
+			childEvents = append(childEvents, childEvent)
+		}
+	}
+	// sort childEvents by origin_server_ts in ASC or DESC depending on recent_first
+	sort.SliceStable(childEvents, func(i, j int) bool {
+		if recentFirst {
+			return childEvents[i].OriginServerTS().Time().After(childEvents[j].OriginServerTS().Time())
+		}
+		return childEvents[i].OriginServerTS().Time().Before(childEvents[j].OriginServerTS().Time())
+	})
+	if len(childEvents) > limit {
+		return childEvents[:limit], nil
+	}
+	return childEvents, nil
+}
+
+func walkThread(ctx context.Context, db Database, limit int) ([]*gomatrixserverlib.HeaderedEvent, bool) {
+	return nil, false
+}
+
+func getEventIfVisible(ctx context.Context, eventID, userID string) *gomatrixserverlib.HeaderedEvent {
+	return nil
+}

internal/mscs/msc2836/storage.go

@@ -13,11 +13,13 @@ import (
 type Database interface {
 	// StoreRelation stores the parent->child and child->parent relationship for later querying.
 	StoreRelation(ctx context.Context, ev *gomatrixserverlib.HeaderedEvent) error
+	ChildrenForParent(ctx context.Context, eventID string) ([]string, error)
 }
 
 type Postgres struct {
-	db                 *sql.DB
-	insertRelationStmt *sql.Stmt
+	db                          *sql.DB
+	insertRelationStmt          *sql.Stmt
+	selectChildrenForParentStmt *sql.Stmt
 }
 
 func NewPostgresDatabase(dbOpts *config.DatabaseOptions) (Database, error) {
@@ -39,6 +41,11 @@ func NewPostgresDatabase(dbOpts *config.DatabaseOptions) (Database, error) {
 	`); err != nil {
 		return nil, err
 	}
+	if p.selectChildrenForParentStmt, err = p.db.Prepare(`
+		SELECT child_event_id FROM msc2836_relationships WHERE parent_event_id = $1
+	`); err != nil {
+		return nil, err
+	}
 	return &p, err
 }
 
@@ -51,10 +58,15 @@ func (p *Postgres) StoreRelation(ctx context.Context, ev *gomatrixserverlib.Head
 	return err
 }
 
+func (p *Postgres) ChildrenForParent(ctx context.Context, eventID string) ([]string, error) {
+	return childrenForParent(ctx, eventID, p.selectChildrenForParentStmt)
+}
+
 type SQLite struct {
-	db                 *sql.DB
-	insertRelationStmt *sql.Stmt
-	writer             sqlutil.Writer
+	db                          *sql.DB
+	insertRelationStmt          *sql.Stmt
+	selectChildrenForParentStmt *sql.Stmt
+	writer                      sqlutil.Writer
 }
 
 func NewSQLiteDatabase(dbOpts *config.DatabaseOptions) (Database, error) {
@@ -77,6 +89,11 @@ func NewSQLiteDatabase(dbOpts *config.DatabaseOptions) (Database, error) {
 	`); err != nil {
 		return nil, err
 	}
+	if s.selectChildrenForParentStmt, err = s.db.Prepare(`
+		SELECT child_event_id FROM msc2836_relationships WHERE parent_event_id = $1
+	`); err != nil {
+		return nil, err
+	}
 	return &s, nil
 }
 
@@ -89,6 +106,10 @@ func (s *SQLite) StoreRelation(ctx context.Context, ev *gomatrixserverlib.Header
 	return err
 }
 
+func (s *SQLite) ChildrenForParent(ctx context.Context, eventID string) ([]string, error) {
+	return childrenForParent(ctx, eventID, s.selectChildrenForParentStmt)
+}
+
 // NewDatabase loads the database for msc2836
 func NewDatabase(dbOpts *config.DatabaseOptions) (Database, error) {
 	if dbOpts.ConnectionString.IsPostgres() {
@@ -115,3 +136,20 @@ func parentChildEventIDs(ev *gomatrixserverlib.HeaderedEvent) (parent string, ch
 	}
 	return
 }
+
+func childrenForParent(ctx context.Context, eventID string, stmt *sql.Stmt) ([]string, error) {
+	rows, err := stmt.QueryContext(ctx, eventID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close() // nolint: errcheck
+	var children []string
+	for rows.Next() {
+		var childID string
+		if err := rows.Scan(&childID); err != nil {
+			return nil, err
+		}
+		children = append(children, childID)
+	}
+	return children, nil
+}